Carl hettwig



UNITED STATES PATENT OFFICE.

CARL HETTVVIG, OF BERLIN AND FRITZ HEOKNER, OF BRAUNSOHXVEIG, GERMANY.

PROCESS OF PRODUCING ORNAMENTAL DESIGNS UPON WOOD.

SPECIFICATION forming part of Letters Patent No. 439,658, dated November4, 1890. Application filed February 21, 1890. fierial No. 841,361. (Nospecimens.)

To all whom it may concern.-

Be it known that we, CARL HETTWIG and FRITZ HECKNER, subjects of theEmperor of the German Empire, residing, respectively, at Berlin andBraunschweig, in the German Empire, have invented certain new and usefulImprovements in Process for Producing Orna mental Designs upon Wood, ofwhich the following is a specification.

This our invention relates to a new process for tinging the naturalsurface of wood or producing thereon picturesque designs of differentshades from a light-brown to a dark-brown color that will not fade fromexposure to light or to the changes of the weather. This processconsists in the discovery of certain chemicals to be applied insuccessive order upon the natural surface of the wood and then thesotreated surface to be eXposetLto the chemical action of the daylight.

It is a well-known process 'to coat the surface of metal, stone, or of amaterial of organic origin and of a homogene nature with a layer ofvarnish and then to tinge the open spots or etchings with an acidiferousor coloring liquid for bringing forth a design upon the thus treatedsurfaces. For producing, however, an ornamental design upon the naturalsurface of wood has had its difliculties, caused by the organic cellularconstruction of wood. The varnishes for etchings are generally of adiaphanous and frequently of a coloring nature, and therefore must beremoved after having served their purpose. For wood this is notpractical, because every mechanical operation of removal is liable toinjure the surface of the wood, While adissolving liquid in washing offthe varnish is apt to soak into the wood andrender its surface with anunclean appearance. It has been found necessary, therefore, to provide avarnish for coating the wooden surface around the spots to be tinged orcolored that is colorless and transparent and will not require removal,but contrary to remain as an advantageous protector and which will notproduce a luster or burnish like the usual varnishes do. The varnish wehave discovered to have the aboved'esired properties consists of astrong solution of caoutchouc in chloroform; and for the purpose ofpreventing the solutions applied for bringing forth the design fromspreading beyond the outlines of the design by running out into thefibers of the wood we previously soak the surfaces with a solution ofalum in the same manner as is usual for wood to be painted upon. Afterthe surfaces of the wood have been thus treated with alum and theoutlines of the design have been drawn or marked thereon in any usualmanner, the quickly-drying caoutchouc varnishis applied in properconformity with the design upon all parts of the wooden surface not tobe colored. Now the unvarnished surfaces of the wood are to be soakedwith a solution of bi chromate of copper, (cuprum bichromicum,) andafter this solution has been well absorbed, but before it has becomedry, a solution of pyrogallic acid is applied. The so-treated Woodensurface, still insignificantly showing the design, is now exposed to thedaylight, which slowly will bring forth a durable and chemically almostindestructible union between the bichromate of copper and the pyrogallicacid by chemical transformation under cooperation of the fibers of thewood, and within about twenty four hours will be brought forth upon thetinged surfaces a more or less dark-brown color.

The two ti'nging solutions can be made and applied in differentproportions-that is, from one part of salt or acid in one hundred partsof distilled water up to the most concentrated solutions. With astronger solution of bichromate of copper and thereupon a weakersolution of pyrogallic acid we obtain greenishplaying color shades; andotherwise, again,a weaker solution of bichromate of copper combined witha stronger solution of pyrogallic acid will produce a reddish brown.Weak solutions in general will produce a lighter coloring and strongersolutions darker colors, and thus in proportion as solutions ofdifferent strength are applied for different portions the design can beshaded, and thereby wonderful effects can be produced. After the actionof the daylight thereon the work is completed.

What we claim is 1. The process of tinging the natural surinchloroform,next for bringing forth the design in color the applying of asol utjon of bichroniai'e of copper, and upon this again a solution ofpyrogxallic acid,and finally exposing the so-t-reated surfaces to thedaylight, all substantially as set forth.

In testimony whereof We affix our signatures in presence of twoWitnesses.

CARL llE'lTWIG. FRITZ IIECKNER. Witnesses:

FREDK. V. CROSBY, ULRICH R. MAERZ.

